Another Serologic Type of Streptococcic Bacteriophage

The Bacteriophages of Streptococcus pyogenes

The bacteriophages of Streptococcus pyogenes (group A streptococcus) play a key role in population shaping, genetic transfer, and virulence of this bacterial pathogen. Lytic phages like A25 can alter population distributions through elimination of susceptible serotypes but also serve as key mediators for genetic transfer of virulence genes and antibiotic resistance via generalized transduction. The sequencing of multiple S. pyogenes genomes has uncovered a large and diverse population of endogenous prophages that are vectors for toxins and other virulence factors and occupy multiple attachment sites in the bacterial genomes. Some of these sites for integration appear to have the potential to alter the bacterial phenotype through gene disruption. Remarkably, the phage-like chromosomal islands (SpyCI), which share many characteristics with endogenous prophages, have evolved to mediate a growth-dependent mutator phenotype while acting as global transcriptional regulators. The diverse population of prophages appears to share a large pool of genetic modules that promotes novel combinations that may help disseminate virulence factors to different subpopulations of S. pyogenes. The study of the bacteriophages of this pathogen, both lytic and lysogenic, will continue to be an important endeavor for our understanding of how S. pyogenes continues to be a significant cause of human disease.

Bacteriophages induced from lysogenic root canal isolates of Enterococcus faecalis

INTRODUCTION

Bacterial viruses play crucial roles in the pathogenesis of many systemic diseases. They are known to inhabit the oral cavity, both as free virions and as prophages in lysogenic bacterial strains; however, there has been no report of bacteriophages in endodontic infections. In this study, we sought to detect, isolate, and describe temperate bacteriophages harbored by Enterococcus faecalis strains isolated from endodontic infections.

METHODS

Ten E. faecalis strains were isolated from root canals of teeth undergoing retreatment following unsuccessful endodontic therapy. Mitomycin C was used to induce any prophages present in the bacterial isolates. The induced phages were purified and examined using electron microscopy. The DNA extracted from one of the phage isolates was subjected to restriction endonuclease digestion and agarose electrophoresis analysis.

RESULTS

Lysogeny was demonstrated in 4 of the 10 E. faecalis strains. Three of the lysogenic strains yielded phages exhibiting a Siphoviridae morphology, with long, non-contractile tails 130 nm in length, and spherical/icosahedral heads 41 nm in diameter. The virus induced from the fourth lysogenic E. faecalis strain had a contractile tail characteristic of Myoviridae. Restriction endonuclease analysis of NsiI and NdeI DNA fragments from one of the Siphoviridae phage isolates (phage phiEf11) indicated a genome size of approximately 41 kbp.

CONCLUSION

This is the first report of lysogenic bacteria and their inducible viruses in infected root canals.

324. The heat resistance of the bacteriophages of cheese starter with observations on the estimation of phage concentration

The heat resistance, in milk, of bacteriophages attacking strains of lactic streptococci isolated from cheese starters has been determined. Active phages did not usually survive a temperature of 75°C. for 7½ min. but many phages were not destroyed by heating for 50–60 min. at 65–67°C. and most survived at 70°C. for 10–15 min. The practical implications of these findings in the ‘sterilization’ of milk for starter making have been discussed. Growth in yeast dextrose broth was found to be superior to methylene blue reduction for the demonstration of residual phages after heating.

CHARACTERIZATION OF ENTEROCOCCUS BACTERIOPHAGES FROM THE SMALL INTESTINE OF THE RAT

Rogers, C. G. (University of Wisconsin, Madison) and W. B. Sarles. Characterization of enterococcus bacteriophages from the small intestine of the rat. J. Bacteriol. 85:1378-1385. 1963.-Enterococcus bacteriophages were isolated by an enrichment procedure from the contents of the small intestines of Sprague-Dawley white rats. After purification by single-plaque isolation, the phages were maintained in Tryptose broth by propagation on strains of Streptococcus faecalis var. zymogenes of similar intestinal origin. The presence of two phage strains was suggested from host range studies, and confirmed by antiserum neutralization tests, whereby the bacteriophages were placed in two distinct, but serologically related, groups. When the characteristics of one phage from each group were studied, differences were observed in antigenic properties, as shown by the ability to stimulate antibody production in rabbits, and in single-step growth characteristics. At 32 C, the latent period was 21 min, and the burst size was 88 plaque-forming particles (PFP) for phage 1; and 34 min and 147 PFP for phage 2. The bacteriophages were similar in temperature of inactivation, sensitivity to pH, and in rates of adsorption to host cells (K = about 2 x 10(-9) ml/min at 32 C). In electron micrographs, the viruses were characterized by slightly elongated heads and long tails, and resembled one another closely. The dimensions of the phage particles were similar to those reported for other phage-host systems within the genus Streptococcus.

Phage typing scheme for group D streptococci isolated from human urogenital tract

Streptococci of Lancefield group D were isolated from 52.2% of pharyngeal, 55.5% of urethral, 56.6% of endocervical, and 75.4% of ano-rectal specimens. Seventeen phages isolated from sewage and urogenital specimens were selected for phage typing. Four of these lysed only the strains of Streptococcus faecalis and its variety liquefaciens. Another six phages lysed only the strains of Streptococcus faecium and its variety durans. With the help of seven bacteriophages, 346 of 384 (90.1%) strains of S. faecalis and its variety liquefaciens could be classified into 27 types. Similarly, with the help of 10 other bacteriophages, 97 of 117 (82.9%) strains of S. faecium and its variety durans could be grouped into 22 types. In 72 of 87 (82.7%) cases, similar phage types were obtained at different culture sites of the same individual.

Intergroup phage reactions and transduction between group C and group A streptococci

In a study of intergroup reactions, four virulent Group A streptococcal phages were found to form plaques in high titer on lawns prepared from a number of Group C streptococcal strains. Whether the phages were propagated on the homologous (Group A) strain or a heterologous (Group C) strain did not appear to influence consistently the plaque-forming efficiency on lawns prepared from a homologous (Group A) or a heterologous (Group C) strain or to alter significantly the percent of Group C strains which showed plaque formation. Considerable variability was found in the ability of temperate phages to lyse strains of a heterologous group. A single Group C indicator strain was lysed by a high percentage of freshly induced temperate Group A phages. A single temperate Group C phage lysed a significant proportion of Group A strains when freshly induced or when propagated on a Group A strain. Intragroup transduction of streptomycin resistance was demonstrated between Group C strains. Intergroup transduction of streptomycin resistance and also bacitracin resistance was achieved between Group C and Group A streptococci. These observations provide evidence that Group A streptococci can serve as recipients in intergroup transmission of genetic information. Ultraviolet irradiation of the transducing lysate and lowering the propagation temperature of the transducing lysate increased the frequency of transduction in both the intragroup and intergroup transduction systems.